Multiple observer and single observer geolocation systems that monitor an emitter's signals to determine its location are known in the art. The monitoring system makes multiple observations of the emitter signal at multiple locations and measures characteristics of the received signals and processes these measurements to predict the location of the emitter. Various characteristics of the emitter's signal can be measured including angle of arrival, time of arrival, relative phase, etc. The accuracy and precision of the geolocation system is dependent on the accuracy and precision of various factors, including the emitter signal measurements, and the knowledge of the detector locations.
Multiple observer geolocation systems can make multiple observations of an emitter's signals from multiple locations simultaneously and can therefore provide nearly instantaneous geolocation of an emitter detected by the multiple observers. Multiple observer systems generally rely on time difference of arrival and/or Doppler difference of arrival measurements. However, multiple observer systems require station keeping, precision clocks and a high degree of synchronization to select the desired signal of interest.
Single observer geolocation systems do not require the precise synchronization of multiple observer systems but they require time to collect observations of the emitter signal from multiple locations. Single observer systems generally rely on angle of arrival schemes using amplitude difference of arrival, phase difference of arrival, as well as, time difference of arrival and/or Doppler difference of arrival measurements. In the past, single observer systems were generally less accurate than multiple observer systems.
A long baseline interferometer antenna system is a system in which the separation between the end elements in an array of detectors is some large number of wavelengths. The length of this separation, or the distance between end elements, is referred to as the interferometer baseline. Interferometer antenna arrays typically are sparse having only a few elements compared to a full array where the elements are typically spaced at half wavelength intervals.